I had the plans copied and 30% reduced so the model will be about
1m40. It amounts to a scale of 1:14.2.

I sawed the ribs from 1cm thick MDF. I always sawed two plates of MDF
at the same time, giving symmetric ribs for both sides of the boat.
This had to be done this way because you only get one side of the boat
in the drawing.
I bought a motorized saw just for this job. cutting about 64 ribs
by hand is not my idea of a hobby.

both ribs were then positioned using a 1cm MDF "side view".
I glued copies of the plan to the MDF and cut out the profile.

The ribs were spaced and held by M5 threaded rod. So I had the
profile, and the left and right set of ribs.
Then I drilled holes thru the profile, just aboove and below where
the rods are, and tied the halves together with tiewraps, clamping the
side view profile inbetween. The rod was just flexible enough to align
the ribs with some precision.

I used polyurethane foam to fill up the spaces and make a solid
plug. polyurethane foam is polyester resistant, and I did not have to
find foam plates of the proper thickness.
I tried on a test-rig first.
It turned out quite nice, but the foam had bent the ribs about a
millimeter outwards.
the foam remains rather soft, but I plan to apply a hard shell
by means of polyurethane yacht varnish.

when foaming the plug, I made sure to
foam the outer ribs first, and work towards the middle ribs
It's impressive stuff, that foam. I made a makeshift
dam to keep the foam where I needed it.

then some crude sawing, cutting and coarse sanding, and it came out
like this :

using a third bottle of foam, after filling the remaining gaps
the current result is
A nice side-effect of the foam is that it also glues the ribs to the profile.

Next steps are filing and sanding the MDF ribs exact,
then plastering, then varnish, then plastering with polyester.
after that the scary stuff begins (i.e. moldmaking).

Last edited by raalst on Wed Jul 01, 2009 5:15 pm, edited 20 times in total.

the gypsum will enable me to smooth the surface to a degree.
the lower part is already sanded, now the upper part must be
sanded.
After that, some polyester coating will be applied and then the
finer smoothing starts.

I practiced my first glassing today on another project. seems
not to involve rocket science. Might be beginners luck though

I skin the foam with glass and resin, then use polyester filler and glazing putty for the final finish. I don't like using plaster- tried it before and found it lacking in strength, plus it takes a while to fully harden off.

However you're method will work, but I'd skin it with resin and glass at the nearest opportunity, as the finish will be very vulnerable up until that point.